1. Field
The disclosed concept relates generally to electrical systems and, more particularly, to electrical systems such as, for example, switchgear systems. The disclosed concept also relates to electrical switching apparatus assemblies for switchgear systems.
2. Background Information
Electrical switching apparatus used in power distribution systems are often mounted within a switchgear enclosure either individually or in combination with other switchgear (e.g., without limitation, circuit switching devices and circuit interrupters such as circuit breakers, contactors, motor starters, motor controllers and other load controllers).
Some electrical switching apparatus such as, for example, some medium-voltage and low-voltage circuit breakers, can be relatively large. In order to facilitate movement (e.g., installation; removal; maintenance), some circuit breakers are commonly coupled to draw-out mechanisms which permit such circuit breakers to be drawn out of a corresponding compartment or cell of the switchgear enclosure. Accordingly, such circuit breakers are commonly known in the art as “draw-out” circuit breakers. The draw-out circuit breaker can be drawn (e.g., racked) into and out of a connected position wherein the primary disconnect contacts of each circuit breaker pole engage with the mating stabs at the rear of the cell. Racking into the connected position is typically accomplished with a manually or electrically rotated jackscrew, worm gear, or other known or suitable mechanism.
ANSI rated medium voltage draw-out circuit breakers are designed to withstand predetermined short circuit currents for predetermined durations. Short circuit testing is conducted with the electrical power contained within the prescribed electrical current paths. Arc resistant medium voltage draw-out circuit breakers must pass more rigorous testing where an electrical arc is artificially initiated between the circuit breaker phases, outside of the prescribed electrical current paths. The resulting explosion of superheated gasses and vaporized components must be managed in such a way as to maintain the arc and the circuit breaker within the switchgear enclosure while the rapidly expanding pressure is directed and expelled in a controlled manner.
Typically, the circuit breaker is latched within the corresponding compartment or cell of the switchgear enclosure via spring-loaded retaining pins extending laterally outwardly from the opposing sides of the circuit breaker to engage corresponding slots in the opposing side walls of the switchgear enclosure compartment or cell. This system is sufficiently robust to withstand standard switchgear ratings. However, the high pressure explosion associated with arc resistant circuit breakers testing causes the side walls of the switchgear enclosure compartment or cell to react by expanding (e.g., bending away). Such expansion can displace the slots in the compartment causing them to unintentionally release the retaining pins. Thus, the potential exists for the circuit breaker to be ejected from the switchgear enclosure compartment.
There is, therefore, room for improvement in switchgear systems and in electrical switching apparatus assemblies therefor.